Malaria is a disease with a wide spectrum of clinical severity. Individuals infected with Plasmodium falciparum can have asymptomatic parasitemia, incidental parasitemia (parasitemia unrelated to clinical symptoms), uncomplicated malaria, or life-threatening cerebral malaria. Markers of disease severity in both the host and the parasite remain elusive. One phenomenon widely held to correlate with severity is sequestration - the binding of infected erythrocytes to endothelial cells in the microvasculature. Although this binding takes place in multiple vascular beds, the heaviest sequestration appears in the brain, and is postulated to lead to the pathology seen in cerebral malaria. This proposal combines new technology and access to a unique patient population in an attempt to better model sequestration in an in vitro setting. The new system is enhanced by the use of: 1) primary endothelial cells from patients dying of malaria or other diseases, 2) fresh parasite isolates taken directly from malaria patients, and 3) a novel microfluidics chamber. The combination of these three elements will greatly increase the ability to accurately represent the sequestration phenomenon in vitro. This system will be used to investigate the role sequestration plays in determining disease severity. I will address the following two questions: 1) What is the relative role of parasite heterogeneity in determining disease severity? 2) What is the basis of variability in cytoadherence among different organs? The novelty of this proposal lies in the ability to obtain parasite and endothelial cell samples directly from exquisitely well characterized patients suffering from a range of malaria disease. This patient population, coupled with the ability to bring a new technology, the microfluidic chamber, to an area of malaria endemicity, allows me to address important questions regarding disease pathogenesis, questions that previously have been unable to be addressed. With my background in malaria research, my experience at a malaria research field site, and my interest in developing accurate in vitro model systems, the training and support provided by this award would greatly aid in my career development goals of becoming an independent investigator.